This invention relates to digital loop carrier transmission systems.
In digital loop carrier transmission systems, bidirectional transmission takes place between end users and a local digital switch at a central office through some access system such as a remote terminal. It is generally desirable for local digital switches to be capable of routing calls among end users even when links with other local digital switches are inoperative. In the modernization of rural telephone equipment, this feature can be assured by replacing old switches with new switches. However, this is a fairly expensive proposition.
A less expensive alternative would be to provide emergency access among end users served by an access system which can include one or more remote terminals.